The traditional internal combustion engine relies on connecting rods for transmitting combustion power from a piston main body to a crankshaft of the engine, thereby converting the linear motion of the piston main body to rotational motion at the crankshaft. Combustion power is generated from the intermittent ignition of a combustible such as gasoline that is injected into the combustion chamber, which creates extreme pressures that are applied to the piston and connecting rod. In particular, the interface between the piston pin bore of the connecting rod and the piston pin may experience substantially continuous radial loads during operation even though only a limited amount of a lubricant may be available for reducing contact friction at the interface.
In an attempt to more evenly distribute radial loads across the piston pin bore surface, the piston pin bore surface may be profiled such that the piston pin bore better accommodates bending of the piston pin under load. However, this may undesirably also reduce the limited amount of lubricant present between the piston pin and the piston pin bore, as the piston pin may generally “squeeze” lubricant out of the interface during piston pin bending. Efforts to improve lubrication of the joint, e.g., by providing a bearing with or without undulations between the piston pin and piston pin bore or by machining undulations in the piston pin bore surface or bearing that allow lubricant to remain within the piston pin and piston pin bore interface during pin deflection, are generally costly and increase part count and/or complexity of the manufacturing process.
Accordingly, there is a need for a connecting rod having an improved lubricated interface between the connecting rod and piston pin while still distributing piston pin loads to minimize connecting rod and piston pin wear and minimizing production complexity.